Improving Memory While You Are Sleeping:

Auditory Closed-Loop Stimulation of the Sleep Slow Oscillation Enhances Memory via Enhancement of Hippocampal Consolidation

Here is a video which explains how Brain rhythms regulate information processing in different states to enable learning and memory formation.

And even more interestingly it shows how they can intervene with synchonrizing, reinforcing auditory waves during sleep to enhance memory function and performance the next day by means of the improved consolidation caused by the boost from the auditory stimulation

The researchers explain and show how in sleeping humans auditory stimulation in phase with the ongoing rhythmic occurrence of slow oscillation up states profoundly enhances the slow oscillation rhythm, phase-coupled spindle activity, and, consequently, the consolidation of declarative memory